We jad a junior to train while we all WFH, but he was a very receptive and smart guy, so it was kind of easy. The last stage of code review, we would go through all changes together in a meeting. I would explain the reasons something may be a bad idea (e.g. harder to maintain later on). Other things were also handled in meetings, so i didn't feel it too different from what I'd do in the office, such as designs/whiteboarding.

This does require enough capacity from seniors, though.

In short, it can work, though some people may prefer face to face contact, and the organization/availability has to allow for some hand holding.